The present invention is directed to a quad flat package (QFP) type semiconductor device and, more particularly, to a QFP device have an additional row of external electrical contacts.
Semiconductor device packaging fulfills basic functions such as providing electric connections and protecting the die against mechanical and environmental stresses. A surface mount semiconductor device has exposed electrical contacts that allow it to mounted on a support, such as a printed circuit board (PCB), for example, where its exposed electrical contacts provide for electrical communication with the PCB or with other circuitry or devices via the PCB. That is, the exposed electrical contacts of the device can be soldered directly to corresponding electrical contact pads on the support, providing mechanical attachment as well as electrical connections. Semiconductor devices are commonly packaged for surface mounting by encapsulating one or more semiconductor dies, the encapsulation process covers the die or dies with a molding compound.
The semiconductor device commonly has an electrically and thermally conductive metal flag (also called die pad or paddle), which participates in cooling the device, whether or not the flag is exposed at the surface of the encapsulation. It is common to facilitate manufacturing operations by performing many of the operations on an array of the semiconductor dies mounted on an array of flags that are linked together, the links being severed during a singulation process. The links are typically provided by a frame structure (e.g., an array of lead frames), which has an array of the flags connected by tie bars to frame members that are removed or cut off and discarded during singulation. The frame structure may also include sets of the exposed leads and electrical contacts that are supported directly or indirectly by the frame members and/or the flags, until the dies are encapsulated, and then the exposed leads and electrical contacts isolated from each other during singulation. This technique is applicable to devices where the leads and electrical contacts are disposed at the periphery of the flag and the semiconductor die, on two opposite sides or around all four sides.
In one type of surface mount semiconductor device, the flag is exposed at its bottom face but in another type the flag as well as the die are embedded in the mold compound. In one type of package, known as quad flat no-lead (QFN), the exposed electrical contacts are positioned in the bottom face of the body of the device at or close to its edge surface. In a QFP, exposed leads project from the edge surface of the body of the device and down to the level of the bottom face of the device in a gull-wing or J-shape configuration.
Various techniques are available for connecting the exposed electrical contacts of the device internally with electrical contact pads of the semiconductor die. In a wire bond package, typically the back face of the die is mounted on the flag and the contact pads of the die on its active face are connected to the exposed electrical contacts of the package with bond wires.
Continued reduction in the size of semiconductor devices and increase in their complexity and functionality result in a need for an increase in the number of exposed electrical contacts and a reduction in the spacing between the electrical contacts and the spacing between the bond wires. A QFP can include one or more rows of electrical contacts exposed in the bottom face of the device in addition to the exposed leads projecting from the edge surface. It would be desirable to allow for more exposed electrical contacts.